Color-blind persons have difficulty distinguishing various colors. Persons whose color vision is impaired include, for example, those who confuse reds and greens (e.g., either protanopia: having defective red cones or deuteranopia: having defective green cones). Jennifer Birch, Diagnosis of Defective Color Vision, Butterworth Heinman (2002). For these people visual discrimination of color-coded data is practically impossible when green, red or yellow data is adjacent. In the color space of such persons, the red-green hue dimension is missing, and red and green are both seen as yellow; they have only the yellow-blue dimension. Even people with normal color vision can, at times, have difficulty distinguishing between colors. As for elderly persons, as a person ages clouding of the lenses of their eyes tends to occur, due, for example, to cataracts. The elderly often experience changes in their ability to sense colors, and many see objects as if they have been viewed through yellowish filters. Additionally, over time ultraviolet rays degenerate proteins in the eye, and light having short wavelengths is absorbed and blue cone sensitivity is thereby reduced. As a result, the appearance of all colors changes, yellow tending to predominate, or a blue or a bluish violet color tends to become darker. Specifically, “white and yellow,” “blue and black” and “green and blue” are difficult to distinguish. Similarly, even a healthy individual with “normal” vision can perceive colors differently when they are at an altitude that is greater than they are normally used to, or under certain medications.
To overcome the inability to distinguish colors, such individuals become adept at identifying and learning reliable cues that indicate the color of an object, such as by knowing that a stop sign is red or that a banana is typically yellow. However, absent these cues, the effect of being color-blind is that they are often unable to reliably distinguish colors of various objects and images, including in cases where the color provides information that is important or even critical to an accurate interpretation of the object or image. Common examples of such objects and images include lighted and non-lighted traffic signals, and pie-charts/graphs of financial information and maps. Moreover, with the proliferation of color computer displays, more and more information is being delivered electronically and visually and usually with color coded information.
To address the fact that important information may be color coded, engineers and scientists have developed a number of devices to aid a color-blind person. For example, U.S. Pat. No. 4,300,819 describes eyeglasses for distinguishing colors using one colored and one clear lens. Similarly, U.S. Pat. No. 4,998,817 describes a corneal contact lens for distinguishing of colors, which is clear except for a thin red exterior layer covering the area admitting light to the pupil.
Although such devices provide some benefit, they are cumbersome to use and have limited effectiveness in that only one color is adjusted, and the user cannot expand or change the manner in which the device alters the perceived color space.
Thus, a user viewing a pie chart that includes a plurality of colors that are outside of the perceptible color space of his or her vision, will have only a moderately improved understanding of the information being conveyed in the pie chart. Therefore, a great load is imposed on such persons when they must read or edit data using a color computer display terminal. In addition, these users cannot locate information on a screen that is displayed using certain colors or color combinations, and thus might not be able to read important notices. For example, when such a user employs a service or resource provided via the Internet, such as an electronic business transaction, or an on-line presentation, it may be that important information or cautionary notes are displayed using characters in colors that the individual may not be able to distinguish.
Accordingly, there is a need for improved systems for aiding in the identification of colors and color-coded information.